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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <condition_variable>
#include <functional>
#include <memory>
#include <mutex>
#include <unordered_map>
#include <vector>
#include "platform/api/time.h"
#include "platform/base/error.h"
#include "platform/base/macros.h"
#include "platform/impl/socket_handle.h"
namespace openscreen {
// The class responsible for calling platform-level method to watch UDP sockets
// for available read data. Reading from these sockets is handled at a higher
// layer.
class SocketHandleWaiter {
using SocketHandleRef = std::reference_wrapper<const SocketHandle>;
enum Flags {
kReadable = 1,
kWriteable = 2,
class Subscriber {
virtual ~Subscriber() = default;
// Provides a socket handle to the subscriber which has data waiting to be
// processed.
virtual void ProcessReadyHandle(SocketHandleRef handle, uint32_t flags) = 0;
explicit SocketHandleWaiter(ClockNowFunctionPtr now_function);
virtual ~SocketHandleWaiter() = default;
// Start notifying |subscriber| whenever |handle| has an event. May be called
// multiple times, to be notified for multiple handles, but should not be
// called multiple times for the same handle.
void Subscribe(Subscriber* subscriber, SocketHandleRef handle);
// Stop receiving notifications for one of the handles currently subscribed
// to.
void Unsubscribe(Subscriber* subscriber, SocketHandleRef handle);
// Stop receiving notifications for all handles currently subscribed to, or
// no-op if there are no subscriptions.
void UnsubscribeAll(Subscriber* subscriber);
// Called when a handle will be deleted to ensure that deletion can proceed
// safely.
void OnHandleDeletion(Subscriber* subscriber,
SocketHandleRef handle,
bool disable_locking_for_testing = false);
// Gets all socket handles to process, checks them for readable data, and
// handles any changes that have occured.
Error ProcessHandles(Clock::duration timeout);
struct ReadyHandle {
SocketHandleRef handle;
uint32_t flags;
// Waits until data is available in one of the provided sockets or the
// provided timeout has passed - whichever is first. If any sockets have data
// available, they are returned.
virtual ErrorOr<std::vector<ReadyHandle>> AwaitSocketsReadable(
const std::vector<SocketHandleRef>& socket_fds,
const Clock::duration& timeout) = 0;
struct SocketSubscription {
Subscriber* subscriber = nullptr;
Clock::time_point last_updated = Clock::time_point::min();
struct HandleWithSubscription {
ReadyHandle ready_handle;
// Reference to the original subscription in the unordered map, so
// we can keep track of when we updated this socket handle.
SocketSubscription* subscription;
// Call the subscriber associated with each changed handle. Handles are only
// processed until |timeout| is exceeded. Must be called with |mutex_| held.
void ProcessReadyHandles(std::vector<HandleWithSubscription>* handles,
Clock::duration timeout);
// Guards against concurrent access to all other class data members.
std::mutex mutex_;
// Blocks deletion of handles until they are no longer being watched.
std::condition_variable handle_deletion_block_;
// Set of handles currently being deleted, for ensuring handle_deletion_block_
// does not exit prematurely.
std::vector<SocketHandleRef> handles_being_deleted_;
// Set of all socket handles currently being watched, mapped to the subscriber
// that is watching them.
std::unordered_map<SocketHandleRef, SocketSubscription, SocketHandleHash>
const ClockNowFunctionPtr now_function_;
} // namespace openscreen